1. Field of the Invention
This invention relates to a novel polyhydroxyalkanoate (hereinafter simply xe2x80x9cPHAxe2x80x9d), and also relates to a process for producing the PHA, comprising the step of producing a PHA by the use of a microorganism having the ability to produce the PHA and accumulate it in the bacterial body.
This invention further relates to a charge control agent, a toner binder and a toner for developing electrostatic latent images, used in recording processes which utilize electrophotography, electrostatic recording, magnetic recording or the like, an image-forming method making use of the toner, and an image-forming apparatus therefor. More particularly, it relates to a charge control agent, a toner binder and a toner for developing electrostatic latent images, used in electrophotographic, electrostatic-recording and electrostatic-printing apparatus such as copying machines, printers and facsimile machines, an image-forming method making use of the toner, and an image-forming apparatus therefor. Still more particularly, it relates to a negatively charging charge control agent having higher safety to human bodies and environment, a toner binder and a toner for developing electrostatic latent images, making use of such a charge control agent, an image-forming method making use of the toner, and an image-forming apparatus therefor.
2. Related Background Art
It has hitherto been reported that many microorganisms produce poly-3-hydroxybutyric acid (PHB) or other PHA and accumulate it in the bacterial body (xe2x80x9cHandbook of Biodegradable Plasticsxe2x80x9d, Biodegradable-Plastic Institute, K.K. N-T-S, pp.178-197, 1995). Like conventional plastics, these polymers can be utilized for the production of various products by melt processing or the like. Also, since they are biodegradable, they have an advantage of being completely broken down by microorganisms in the natural world, and by no means remain in natural environment to cause pollution as many conventional synthetic polymeric compounds do. They also have superior adaptability to living bodies and are expected to be applicable as medical flexible members.
It is known that such PHAs produced by microorganisms may have various composition and structure depending on the type of microorganisms used for its production, the composition of culture medium, the conditions for culturing and so forth. Researches on how to control such composition and structure have hitherto chiefly been made from the viewpoint of the improvement in physical properties of PHAs.
(1) In the first place, as biosyntheses of PHAs by the polymerization of a monomer unit having a relatively simple structure, including 3-hydroxybutyric acid (hereinafter simply xe2x80x9c3HBxe2x80x9d), the following cases are available.
(a) Those which contain 3HB and 3-hydroxyvaleric acid (hereinafter xe2x80x9c3HVxe2x80x9d):
U.S. Pat. Nos. 4,393,167, 4,876,331 and 5,200,332.
(b) those which contain 3HB and 3-hydroxyhexanoic acid (hereinafter xe2x80x9c3HHxxe2x80x9d):
U.S. Pat. No. 5,292,860 and Japanese Patent Application Laid-Open No. 7-265065.
(c) those which contain 3HB and 4-hydroxybutyric acid (hereinafter xe2x80x9c4HBxe2x80x9d):
Japanese Patent Application Laid-Open No. 9-191893.
(d) those which contain 3-hydroxyalkanoates having 6 to 12 carbon atoms:
U.S. Pat. No. 5,334,698.
(e) Biosynthesis utilizing a simple fatty acid as a carbon source. Products are substantially the same as those of (d); Appl. Environ. Microbiol., 58(2), 746, 1992.
These are all PHAs each comprised of a monomer unit having an alkyl group in the side chain, i.e., xe2x80x9cusual PHAxe2x80x9d, all synthesized by xcex2-oxidation of hydrocarbons or synthesis of fatty acids from saccharides by the microorganisms.
(2) When, however, broader application of such PHAs produced by microorganisms, e.g., application as functional polymers is taken into account, a PHA in which a substituent other than the alkyl group has been introduced in the side chain, i.e., xe2x80x9cunusual PHAxe2x80x9d is expected to be very useful. As examples of such a substituent, it may include those containing aromatic rings (such as a phenyl group and a phenoxy group), unsaturated hydrocarbons, an ester group, an ally group, a cyano group, halogenated hydrocarbons and epoxides. Of these, researches are energetically made especially on PHAs having aromatic rings.
(a) Those which contain a phenyl group or a partially substituted phenyl group:
Macromol. Chem. Phys., 191, 1957-1965 (1990) and Macromolecules, 24, 5256-5260 (1991) report that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-phenylvaleric acid as a unit, using 5-phenylvaleric acid as a substrate.
Macromolecules, 29, 1762-1766 (1996) reports that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-(4xe2x80x2-tolyl)valeric acid as a unit, using 5-(4xe2x80x2-toyl)valeric acid as a substrate.
Macromolecules, 32, 2889-2895 (1999) reports that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-(2xe2x80x2,4xe2x80x2-dinitrophenyl)valeric acid and 3-hydroxy-5-(4xe2x80x2-nitrophenyl)valeric acid as units, using 5-(2xe2x80x2,4xe2x80x2-dinitrophenyl)valeric acid as a substrate.
(b) Those which contain a phenoxyl group or a partially substituted phenoxyl group:
Macromol. Chem. Phys., 195, 1665-1672 (1994) reports that Pseudomonas oleovorans produces a PHA copolymer of 3-hydroxy-5-phenoxyvaleric acid with 3-hydroxy-9-phenoxynonanoic acid, using 11-phenoxyundecanoic acid as a substrate.
Japanese Patent No. 2,989,175 discloses invention which is concerned with a homopolymer comprised of a 3-hydroxy-5-(monofluorophenoxy)pentanoate (3H5(MFP)P) unit or a 3-hydroxy-5-(difluorophenoxy)pentanoate (3H5(DFP)P) unit, and a copolymer containing at least the (3H5(MFP)P) unit or the (3H5(DFP)P) unit; Pseudomonas putida capable of synthesizing such a polymer; and a process of producing the above polymer by the use of the genus Pseudomonas. It is reported that as its effect a polymer the side-chain terminal of which has a phenoxyl group substituted with 1 or 2 fluorine atom(s) can be synthesized by utilizing a long-chain fatty acid having a substituent and that stereo-regularity (syndiotacticity) and water repellency can be imparted having a high melting point and retaining good processability.
In addition to such fluorine-group-substituted products, cyano-group- or nitro-group-substituted products are also on researches.
Can. J. Microbiol., 41, 32-43 (1995) and Polymer International, 39, 205-213 (1996) report that a PHA containing 3-hydroxy-p-cyanophenoxyhexanoic acid or 3-hydroxy-p-nitrophenoxyhexanoic acid as a monomer unit is produced using octanoic acid and p-cyanophenoxyhexanoic acid or p-nitrophenoxyhexanoic acid as a substrate by the use of Pseudomonas oleovorans strain ATCC 29347 and Pseudomonas putida strain KT 2442.
These reports are useful in order to obtain polymers which all have an aromatic ring in the side chain of PHA, different from the commonly available PHAs having an alkyl group in the side chain, and have physical properties arising therefrom.
(3) As a new category, without limitation merely to changes in physical properties, researches are also made intending to produce a PHA having a suitable functional group in the side chain.
For example, Macromolecules, 31, 1480-1486 (1996) and Journal of Polymer Science: Part A: Polymer Chemistry, 36, 2381-2387 (1998) report that a PHA containing at the side-chain terminal a unit having a vinyl group is synthesized and thereafter the product synthesized is epoxidized with an oxidizing agent and this has enabled synthesis of a PHA containing a highly reactive epoxy group at the side-chain terminal.
Besides the vinyl group, as an example of synthesizing a PHA containing a unit having a thioether (xe2x80x94Sxe2x80x94; a sulfanyl linkage), expected to provide a high reactivity, Macromolecules, 32, 8315-8318 (1999) reports that Pseudomonas putida strain 27N01 produces a PHA copolymer of 3-hydroxy-5-thiophenoxyvaleric acid (3-hydroxy-5-(phenylsulfanyl)valeric acid) with 3-hydroxy-7-thiophenoxyheptanoic acid (3-hydroxy-7-(phenylsulfanyl)heptanoic acid), using 11-thiophenoxyundecanoic acid (11-(phenylsulfanyl)undecanoic acid) as a substrate.
A number of methods are also conventionally known as methods for electrophotography. In general, copied images are obtained by forming an electrostatic latent image on an image-bearing member (photosensitive member) by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a visible image (toner image), transferring the toner image to a transfer medium as occasion calls, and then fixing the toner image to the transfer medium by heating and/or pressing. As methods by which the electrostatic latent image is formed into a visible image, cascade development, magnetic brush development, pressure development and so forth are known in the art. Another method is also known in which, using a magnetic toner and a rotary developing sleeve provided with magnetic poles at the core, the magnetic toner is caused to fly from the developing sleeve to the photosensitive member by the an electric field.
As development methods used when electrostatic latent images are developed, available are a two-component development method making use of a two-component type developer comprised of a toner and a carrier and a one-component development method making use of no carrier and comprised only of a toner.
Here, fine colored particles commonly called a toner are constituted of a binder resin and a colorant as essential components and besides optionally a magnetic material and so forth. As methods for imparting electric charges to the toner, the charging properties of the binder resin itself may be utilized without use of any charge control agent. If that is the case, however, the binder resin has poor charging stability with time and poor moisture resistance. Accordingly, a charge control agent is usually added for the purpose of charge retention and charge control of the toner.
Conventional charge control agents nowadays known in the present technical field include, e.g., as negative charge control agents, azo dye metal complexes, metal complexes of aromatic dicarboxylic acids and metal complexes of salicylic acid derivatives. Also, known as positive charge control agents are Nigrosine dyes, triphenylmethane dyes, organotin compounds such as quaternary ammonium salt dibutyltin oxides of various types, and so forth. Toners containing any of these as charge control agents, however, do not necessarily well satisfy quality characteristics such as charging performance and stability with time in some cases, depending on their composition; the characteristics being required in toners.
For example, toners containing the azo dye metal complexes known as negative charge control agents are on a reasonable level in respect of the highness of charge quantity. However, since the azo dye metal complexes are crystal compounds with a low molecular weight, they may have a poor dispersibility depending on the type of binder resins in which they are to be incorporated. In such as case, the negative charge control agents are not uniformly distributed in the binder resins, and the resultant toners also have a charge quantity distribution lacking in sharpness greatly, so that the images to be obtained may have a low gradation, showing a poor image formation performance. Moreover, the azo dye metal complexes have color tone specific thereto, and hence, under the existing conditions, they are used only in toners with hues limited mainly to black. When such toners are used as color toners, what is of a great problem is that they have not any sharpness of coloring agents which is required in order to obtain images having a high requirement for color tone.
As an example of nearly colorless negative charge control agents, the metal complexes of aromatic dicarboxylic acids are available, which, however, may have a problem of low dispersibility because of the fact that they are not perfectly colorless and that they are crystal compounds with a low molecular weight.
As for the Nigrosine dyes and the triphenylmethane dyes, known as positive charge control agents, they stand colored in themselves, and hence, under the existing conditions, they are also used only in toners with hues limited mainly to black, and also may have no good stability with time when such toners are used in continuous copying. Conventional quaternary ammonium salts may also have an insufficient moisture resistance when incorporated in toners. In such a case, such toners may have so poor a stability with time as not to afford any good images in their repeated use.
In recent years, from the viewpoint of environmental conservation, too, what has become a worldwide subject of discussion is how waste be curtailed and how the safety of waste be improved. Such a subject is likewise discussed also in the field of electrophotography. More specifically, with wide spread of image-forming apparatus, the disposal of printed paper, waste toner after use and copying paper is increasing year by year, and the safety of such waste is also an important subject from the standpoint of the conservation of global environment.
Taking account of such a point, studies are being made on polymer type charge control agents. They include compounds disclosed in, e.g., U.S. Pat. Nos. 4,480,021, 4,442,189 and 4,925,765 and Japanese Patent Application Laid-Open Nos. 60-108861, 61-3149, 63-38958 and 63-88564. Also, in general, as polymer type charge control agents used when toners are made to exhibit negative chargeability, there are many examples in which copolymers of styrene and/or xcex1-methylstyrene with alkyl acrylates or methacrylates or alkyl acrylate or methacrylate amides having sulfonic acid groups are used (Japanese Patent Application Laid-Open Nos. 7-72658 and 8-179564 and Japanese Patent Nos. 2,114,410, 2,623,684 and 2,807,795). Such materials are advantageous in that they are colorless, but must be added in a large quantity in order to ensure charge quantity.
Thus, these compounds do not have any sufficient performance as charge control agents, and have problems on charge quantity, charging-rise performance, stability with time, environmental stability and so forth. Also, considering not only the aspect of function but also any influence on human bodies and environment, it is strongly sought in respect of compounds and organic solvents used in synthesis, too, to provide a safer compound, a safer and milder synthesis process, and a charge control agent which can achieve use of organic solvents in a smaller quantity.
From the viewpoint of environmental conservation, development is being made on resins degradable with time by the action of microorganisms, i.e., biodegradable resins. For example, as stated previously, it has been reported that many microorganisms are capable of producing the biodegradable resin PHA and accumulating it in the bacterial body. It is known that such PHA can have various composition and structure depending on the type of microorganisms used for its production, the composition of culture medium, the conditions for culturing and so forth. Researches on how to control such composition and structure have hitherto chiefly been made from the viewpoint of the improvement in physical properties of PHA. With regard to its application, too, they have already given reasonable actual results especially in the field of materials for medical use. In the field of agriculture, too, the biodegradable resins are used in multifiles, gardening material and so forth, and also in sustained-release agricultural chemicals, fertilizers and so forth. In the field of leisure industry, too, the biodegradable resins are used in fishing lines, fishing articles, golf goods and so forth.
However, considering their wide application as plastics, under the existing conditions they can not still be said to be satisfactory in respect of physical properties. In order to make the PHA utilizable in much wider ranges, it is important to study the improvement of physical properties more widely. For that end, it is essential to make development and research on PHAs containing monomer units of various structures. Meanwhile, the PHA of the type a substituent has been introduced in the side chain can be expected to be expanded as a xe2x80x9cfunctional polymerxe2x80x9d having very useful functions and properties attributable to the properties of the substituent introduced, by selecting according to the desired properties and so forth the substituent to be introduced. Namely, it is also an important subject to make development and research on such a superior PHA that can achieve both such functional factors and the biodegradability.
In the field of electrophotography, too, the application of biodegradable resins to binder resins is proposed especially in the production of toners. For example, U.S. Pat. No. 5,004,664 discloses a toner having as its composition a biodegradable resin, in particular, polyhydroxybutyric acid, polyhydroxyvaleric acid, or a copolymer or blend of these. Japanese Patent Application Laid-Open No. 6-289644 also disclose an electrophotographic toner particularly used for heat-roll fixing, which is characterized in that at least a binder resin contains a vegetable wax and a biodegradable resin (as exemplified by polyesters produced by microorganisms and natural polymeric materials derived from vegetables or animals), and the vegetable wax is added to the binder resin in an amount of from 5 to 50% by weight.
U.S. Pat. No. 5,667,927 also discloses an electrophotographic toner characterized by containing a lactic-acid resin as a binder resin. Japanese Patent Application Laid-Open No. 9-274335 still also discloses a toner for developing electrostatic latent images which is characterized by containing a polyester resin and a colorant; the former being obtained by dehydration polycondensation of a composition containing lactic acid and a tri- or more functional oxycarboxylic acid.
Japanese Patent Application Laid-Open No. 8-262796 also discloses an electrophotographic toner containing a binder resin and a colorant, and is characterized in that the binder resin comprises a biodegradable resin (as exemplified by aliphatic polyester resins) and the colorant comprises a water-insoluble coloring matter. Japanese Patent Application Laid-Open No. 9-281746 still also discloses a toner for developing electrostatic latent images which is characterized by containing a urethanated polyester resin and a colorant; the former being obtained by cross-linking polylactic acid with a tri- or more functional polybasic isocyanate.
In all the electrophotographic toners stated above, biodegradable resins are used as their binder resins, and they are understood to have the effect of contributing to the environmental safeguard and so forth.
However, any report on an example in which biodegradable resins are used in charge control agents is still unknown. Thus, there is room for further progress in respect of the contribution to the environmental safeguard and so forth.
As stated previously, in the PHAs produced by microorganisms, those having various composition and structure are obtained by changing the type of microorganisms used for its production, the composition of culture medium, the conditions for culturing and so forth. However, considering their wide application as plastics, they can not still be said to be satisfactory in respect of physical properties. In order to make the PHA utilizable in much wider ranges, it is important to study the improvement of physical properties more widely. For that end, it is essential to make development and research on PHAs containing monomer units of various structures, on their production processes and on microorganisms capable of producing the desired PHAs efficiently.
Meanwhile, as also stated previously, the PHA of the type a substituent has been introduced in the side chain (the unusual PHA) can be expected to be expanded as a xe2x80x9cfunctional polymerxe2x80x9d having very useful functions and properties attributable to the properties of the substituent introduced, by selecting according to the desired properties and so forth the substituent to be introduced. Thus, it is also an important subject to make development and research on such a superior PHA that can achieve both the functional factors and the biodegradability, on its production process and on microorganisms capable of producing the desired PHA efficiently.
More specifically, where PHAs in the side chains of which various substituents have been introduced are produced by microorganisms, a method is used in which, as is seen in the reports given previously on Pseudomonas oleovorans, an alkanoate having a substituent intended to be introduced is utilized also as a carbon source for proliferation in addition to its utilization as a raw material for polymers.
However, in the method in which an alkanoate having a substituent intended to be introduced is utilized also as a carbon source for proliferation in addition to its utilization as a raw material for polymers, it is expected that an energy source on the basis of the formation of acetyl-CoA by xcex2-oxidation is supplied from the alkanoate. In such a method, the acetyl-CoA can not be formed by xcex2-oxidation unless the substrate has a chain length which is large to a certain extent. Hence, it is of a great problem that the alkanoate usable as the substrate of PHA is necessarily limited. Also, commonly, substrates whose chain length has come short for two methylene chains each as a result of xcex2-oxidation are newly formed, and these are incorporated as monomer units of the PHA. Hence, the PHA synthesized may often be a copolymer comprised of monomer units whose chain length differs for two methylene chains each. In the reports given previously, produced is a copolymer comprised of three monomer units, 3-hydroxy-8-phenoxyoctanoic acid derived from 8-phenoxyoctanoic acid which is a substrate, 3-hydroxy-6-phenoxyhexanoic acid which is a by-product derived from a metabolic intermediate and 3-hydroxy-4-phenoxybutyric acid. In this regard, it is very difficult to use this method when it is intended to obtain a PHA comprised of single monomer units. Moreover, in the method which conditions that an energy source on the basis of the formation of acetyl-CoA by xcex2-oxidation is supplied, microorganisms may proliferate so slowly that it takes a time to synthesize the PHA and that the PHA synthesized tends to be in a low yield. These are also of great problems.
Accordingly, it is considered effective to use a method in which microorganisms are cultured in a culture medium where, in place of the alkanoate having a substituent to be introduced, a medium-chain fatty acid or the like such as octanoic acid or nonanoic acid is made present together (coexistent) as a carbon source for proliferation, and thereafter the PHA is extracted. Such a method is commonly used.
However, according to studies made by the present inventors, the PHA synthesized through xcex2-oxidation, using the medium-chain fatty acid or the like such as octanoic acid or nonanoic acid as the carbon source for proliferation as in the above may be obtained in a low purity, and 50% or more of the polymer obtained is held by 3-hydroxyalkanoic acid monomer units of mcl (hereinafter often simply xe2x80x9cmcl-3HAxe2x80x9d), i.e., the units of xe2x80x9cusual PHAxe2x80x9d, which are monomer units derived from the carbon source for proliferation (e.g., 3-hydroxyoctanoic acid and 3-hydroxynonanoic acid). These mcl-3HA monomer units are polymers which are tacky at normal temperature when composed alone, and may make polymers have a greatly low glass transition temperature (Tg) when mixedly present in a large quantity in the PHA intended in the present invention. Hence, where physical properties of polymers which are hard at normal temperature are to be attained, it is not preferable that the mcl-3HA monomer units are mixedly present.
It is also known that such heterogeneous side-chain structure may obstruct the intramolecular or intermolecular mutual action attributable to the side-chain structure to greatly affect crystallizability or orientationality. For the achievement of improvement in physical properties of polymers and impartment of functional performance thereto, it is of a great problem that such mcl-3HA monomer units are mixedly present. As a means for solving this problem, a purification step for separating and removing any xe2x80x9cunintendedxe2x80x9d monomer units such as the mcl-3HA monomer units derived from the carbon source for proliferation may be provided in order to obtain a PHA constituted of only monomer units having specific substituents. This, however, brings about problems that its operation is complicated and also a greatly low yield may inevitably result. A greater problem is that, where the intended monomer units and the unintended monomer units have formed a polymer, it is very difficult to remove only the unintended monomer units. Especially where it is intended to synthesize a PHA containing such monomer units that have as side-chain structure a group obtained from an unsaturated hydrocarbon, an ester group, an allyl group, a cyano group, a nitro group, a group obtained from a halogenated hydrocarbon or a group into which an epoxide has been introduced, the mcl-3HA monomer units often form a copolymer together with the intended monomer units. Thus, it is very difficult to remove the mcl-3HA monomer units after the synthesis of PHA.
Accordingly, the present inventors have come acknowledged that, when the application to functional polymers is taken into account, it is by all means necessary to make development of a biosynthetic process by which the xe2x80x9cunusual PHAxe2x80x9d can be obtained in a high purity. Thus, it has been considered very useful and important to make development of i) a superior polymer having both the functional performance and the biodegradability as stated above, ii) microorganisms capable of producing such a polymer and accumulating it in the bacterial body, and iii) a process for bio-synthesizing the PHA in a high purity and efficiently.
The present invention is to solve the problems discussed above, and an object of the present invention is to provide a PHA (unusual PHA) containing a monomer unit having a variety of structure, having in the side chain a substituent, which PHA is useful as device materials and medical materials, and provide a process for producing the unusual PHA by utilizing microorganisms, in particular, a process which can obtain the intended xe2x80x9cunusual PHAxe2x80x9d in a high purity with less unintended monomer units mixedly present and can promise a high yield.
As a PHA having a suitable functional group in the side chain and expected to have new function attributable to such a functional group, it is foreseen that, in order to make development of functional PHAs, a PHA having an S atom in the side chain for example will be on research more and more in future because of its highness of reactivity. However, examples of research on such a PHA are very few. Only a report concerning a PHA containing a 3-hydroxy-phenylsulfanylalkanoic acid unit can be exemplified as a related report.
In order to make development of functional PHAs by chemically modifying the side chain of the PHA obtained, it is desired for the PHA to have a side chain such as a thienyl group or a thienoyl group, having a higher reactivity than a phenyl group. However, there has been no report that any PHA concerned with it has been produced.
Taking account of such a subject, another object of the present invention is to provide a novel PHA containing a unit having a thienyl structure in the side chain, and a process for its production.
A further object of the present invention is, in order to solve the above problems in electrophotographic processes, to provide a negatively charging charge control agent which is more highly contributory to the environmental safeguard and so forth from the aspect of function and also has high performances (i.e., high charge quantity, quick rise in charging, good stability with time and high environmental stability), and has been improved in dispersibility, utilizing the novel PHA containing a unit having a thienyl structure in the side chain; and a toner binder comprising such a charge control agent, a toner for developing electrostatic latent images which comprises the charge control agent, and an image-forming method and an image-forming apparatus which make use of the toner for developing electrostatic latent images
Accordingly, aiming at the development of a PHA having in the side chain a functional group, which is useful as device materials and medical materials, the present inventors have repeatedly made investigation of microorganisms having the ability to produce various PHAs and accumulate them in the bacterial body, and extensive researches on a process for producing the desired PHA by using such microorganisms. As a result, they have accomplished the invention as described below. That is, the summary of the present invention is as follows:
The present invention provides a polyhydroxyalkanoate characterized by having in the molecule a unit represented by Chemical Formula (1): 
wherein n may assume any one integral value within the range of from 1 to 8.
The present invention is also a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8): 
wherein n may assume any one integral value within the range of from 1 to 8, 
wherein n may assume any one integral value within the range of from 1 to 8, and polypeptone.
The present invention is still also a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8) and yeast extract.
The present invention is further a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8) and a saccharide.
The present invention is still further a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8) and an organic acid or a salt thereof.
The present invention is still further a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8) and an amino acid or a salt thereof.
The present invention is still further a process for producing a polyhydroxyalkanoate having in the molecule the unit represented by Chemical Formula (1); the process comprising culturing a microorganism in a culture medium containing at least one compound represented by Chemical Formula (7) or (8) and a straight-chain alkanoic acid having 4 to 12 carbon atoms or a salt thereof.
The present inventors have made further extensive studies aiming at the development of a charge control agent which is more highly contributory to the environmental safeguard and so forth and also has high performances. As a result, they have accomplished the present invention.
That is, the present invention is a charge control agent comprising a polyhydroxyalkanoate having in the molecule at least one unit of units represented by Chemical Formula (1): 
wherein n may assume any one integral value within the range of from 1 to 8.
The present invention is also a charge control agent comprising a polyhydroxyalkanoate having in the molecule at least one unit of units represented by Chemical Formula (12): 
wherein n may assume any one integral value within the range of from 1 to 8.
The present invention is still also a toner binder comprising a charge control agent having the above polyhydroxyalkanoate.
The present invention is further a toner for developing electrostatic latent images which comprises a binder resin, a colorant and a charge control agent having the above polyhydroxyalkanoate.
The present invention is still further an image-forming method comprising:
a charging step of applying a voltage to a charging member from its outside to charge an electrostatic-latent-image-bearing member electrostatically;
a latent-image-forming step of forming an electrostatic latent image on the electrostatic-latent-image-bearing member thus charged;
a developing step of developing the electrostatic latent image by the use of a toner for developing electrostatic latent images, to form a toner image on the electrostatic-latent-image-bearing member;
a transfer step of transferring to a recording medium the toner image formed on the electrostatic-latent-image-bearing member; and
a heat fixing step of fixing by heat the toner image held on the recording medium;
wherein the toner for developing electrostatic latent images comprises a binder resin, a colorant and a charge control agent containing the above polyhydroxyalkanoate.
The present invention is still further an image-forming apparatus comprising:
a charging means for applying a voltage to a charging member from its outside to charge an electrostatic-latent-image-bearing member electrostatically;
a latent-image-forming means for forming an electrostatic latent image on the electrostatic-latent-image-bearing member thus charged;
a developing means for developing the electrostatic latent image by the use of a toner for developing electrostatic latent images, to form a toner image on the electrostatic-latent-image-bearing member;
a transfer means for transferring to a recording medium the toner image formed on the electrostatic-latent-image-bearing member; and
a heat fixing means for fixing by heat the toner image held on the recording medium;
wherein the toner for developing electrostatic latent images comprises a binder resin, a colorant and a charge control agent containing the above polyhydroxyalkanoate.